title: BAX activation is initiated at a novel interaction site.
abstract: BAX is a pro-apoptotic protein of the BCL-2 family that is stationed in the cytosol until activated by a diversity of stress stimuli to induce cell death. Anti-apoptotic proteins such as BCL-2 counteract BAX-mediated cell death. Although an interaction site that confers survival functionality has been defined for anti-apoptotic proteins, an activation site has not been identified for BAX, rendering its explicit trigger mechanism unknown. We previously developed stabilized alpha-helix of BCL-2 domains (SAHBs) that directly initiate BAX-mediated mitochondrial apoptosis. Here we demonstrate by NMR analysis that BIM SAHB binds BAX at an interaction site that is distinct from the canonical binding groove characterized for anti-apoptotic proteins. The specificity of the human BIM-SAHB-BAX interaction is highlighted by point mutagenesis that disrupts functional activity, confirming that BAX activation is initiated at this novel structural location. Thus, we have now defined a BAX interaction site for direct activation, establishing a new target for therapeutic modulation of apoptosis.
authors.affiliation: Department of Pediatric Oncology and the Program in Cancer Chemical Biology, Dana-Farber Cancer Institute, 44 Binney Street, Boston, Massachusetts 02115, USA.
authors.forename: Evripidis
authors.initials: E
authors.lastname: Gavathiotis
authors.forename: Motoshi
authors.initials: M
authors.lastname: Suzuki
authors.forename: Marguerite L
authors.initials: ML
authors.lastname: Davis
authors.forename: Kenneth
authors.initials: K
authors.lastname: Pitter
authors.forename: Gregory H
authors.initials: GH
authors.lastname: Bird
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Katz
authors.forename: Ho-Chou
authors.initials: HC
authors.lastname: Tu
authors.forename: Hyungjin
authors.initials: H
authors.lastname: Kim
authors.forename: Emily H-Y
authors.initials: EH
authors.lastname: Cheng
authors.forename: Nico
authors.initials: N
authors.lastname: Tjandra
authors.forename: Loren D
authors.initials: LD
authors.lastname: Walensky
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D051028:bcl-2-Associated X Protein / Q000737:chemistry / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D051028:bcl-2-Associated X Protein